1. Field of the Invention:
This invention relates to polishing apparatus for polishing surfaces of material to be polished with abrasive, and more particularly to polishing apparatus which is suitably used in a so-called varnishing system which shaves off protrusions on surfaces of a magnetic disc without injuring the surfaces or the like.
2. Description of the Related Art
As the polishing apparatus which is used for the varnishing system, a polishing apparatus which includes a lapping tape for polishing a surface of a magnetic disc, a tape supply unit for supplying the lapping tape, a rubber roller for bringing the lapping tape supplied by the tape supply unit into contact with the surface of the magnetic disc, and a pressing unit for pressing the lapping tape to the surface of the magnetic disc with a given pressure by way of a rubber roller is known.
Meanwhile, since the polishing apparatus uses the pneumatic cylinder as the pressing unit, the apparatus has the following drawbacks.
(1) Since the pneumatic pressure is liable to fluctuate, it is difficult to hold the pressing force at a desired level.
(2) It is difficult to adjust the pressing force of the pneumatic cylinder. Particularly, it is difficult to add the minute pressing force in the order of several grams to the lapping tape with the pneumatic cylinder.
(3) The pneumatic cylinder is not adequate to bring the lapping tape into gradual and soft contact with the magnetic disc , and to gradually and softly move the lapping tape away from the magnetic disc.
It is therefore an object of the present invention to provide a polishing apparatus capable of producing a desired pressing force.
According to the present invention, a polishing apparatus comprises:
a abrasive material supply unit (4, 7) for supplying an abrasive material;
a first abrasive material guide member (5) for pressing the abrasive material supplied from the abrasive material supply unit, to a first surface of the material to be polished; and
a pressing unit (6) for pressing the abrasive material to the first surface of the material to be polished with a predetermined pressing force by way of the abrasive material guide member. The pressing unit comprises, a swing lever (51) provided with the abrasive material guide member (5), and a balance adjusting unit (52) which presses the abrasive material to the material to be polished by way of the abrasive material guide member with a desired load determined by adjusting a load applied to the swing lever.